This invention relates to early suppression fast response sprinklers which have large orifices so as to distribute large quantities of water at low working pressures.
Early suppression, fast response (ESFR) sprinklers are designed to provide rapid response to a detected fire hazard by delivering increased water densities in order to satisfy the actual delivered density (ADD) and distribution requirements with various ceiling heights for improved fire suppression in which the ESFR sprinklers are to be used. Conventionally, ESFR sprinklers have had a K factor of 14 and various sprinkler standards have specified K14 as the standard size for ESFR sprinklers. Recently, ESFR sprinklers have been designed with larger orifices, and correspondingly higher K factors, to meet the need for high flow rates at lower fluid pressures, and to avoid the necessity for a booster pump. Factory Mutual Research has established ADD requirements for such ESFR sprinklers having a higher K factor.
The Meyer et al. U.S. Pat. No. 5,829,532 discloses low pressure ESFR sprinklers having nominal K-factors greater than 16 and, specifically, a sprinkler having a K factor of 25 which is capable of delivering at least one hundred gallons per minute at an operating pressure of 20 psi and requiring a minimum pressure of only 15 psi. A particular sprinkler described in that patent has a sprinkler body with an outlet orifice with a minimum diameter of 0.930 inches and includes a pair of support arms extending forwardly and outwardly from the sprinkler body and then laterally inwardly toward the sprinkler axis to form a tubular knuckle supporting a deflector on the side facing the orifice in the sprinkler body. The deflector includes a planar circular plate having a plurality of angularly spaced radial slots of uniform width extending inwardly from the periphery of the deflector to a central region which supports a hemispherical nose piece facing the orifice.
U.S. Pat. No. 5,494,113 discloses a sprinkler having a planar deflector supported by arms similar projecting forwardly and outwardly from a sprinkler body and joined in a deflector support on the opposite side of the deflector from the orifice in the sprinkler body. In that patent, a central deflecting cone is mounted on the deflector facing the sprinkler orifice. U.S. Pat. No. 4,580,729 discloses a sprinkler having arms projecting forwardly and outwardly from the sprinkler body and then inwardly to a conical boss supporting a sprinkler deflector on the side opposite from the sprinkler body, and according to that patent, the half angle of the cone should be in a range from about 5xc2x0 to 50xc2x0. The Reliable Automatic Sprinkler Co. Inc., Model H ESFR Sprinkler has a K factor of 14 and has a circular deflector with radial slots of uniform width and a central nose cone with a nose cone included angle of about 60xc2x0. U.S. Pat. Nos. 2,502,754, 4,553,603, 5,020,601 and 3,998,273 schematically illustrate sprinklers having deflectors with radial slots in which the side of the slots diverge in the outward direction of the slot at substantial unspecified angles.
It has now been found, however, that large orifice, high K factor sprinklers do not provide as efficient water distribution with the same deflector arrangements which are effective with smaller orifice, lower K factor sprinklers.
Accordingly, it is an object of the present invention to provide a large orifice, low pressure ESFR sprinkler which overcomes disadvantages of the prior art.
Another object of the invention is to provide a large orifice, low pressure ESFR sprinkler arrangement providing more efficient water distribution.
A further object of the invention is to provide a large orifice ESFR sprinkler arrangement having a more efficient deflector arrangement and therefore requiring less water at the same pressure as a sprinkler having a higher K factor but nevertheless effective to provide the same protection as a sprinkler having the higher K factor.
An additional object of the invention is to provide an ESFR sprinkler arrangement having a nominal K factor of 22 but providing the same effective water distribution as a conventional sprinkler having a nominal K factor of 25.
These and other objects of the invention are attained by providing an ESFR sprinkler having a sprinkler body with an outlet orifice and a substantially planar deflector disc supported from the sprinkler body and having radial slots with sides diverging outwardly from the inner end and a central projecting member facing the orifice which has a convexly curved surface of revolution. The convex curved surface of the projecting member tends to direct water toward the center of the region beneath the sprinkler while the slots with diverging sides tend to assure good distribution at the outer portions of the region to be protected. Preferably, the slot sides diverge from the center line of the slots at an angle in a range from about 5xc2x0 to 10xc2x0. In addition, the small end of the projecting member is preferably rounded with a spherical radius of about 0.05 inches and is located about 0.5 inch away from the surface of the deflector disc while the large end of the projecting member has a diameter of about 0.55 to 0.65 inches and substantially covers the central region of the deflector inside the inner ends of the deflector slots. In one embodiment the sprinkler has a K factor of 22 and the radius of curvature of the convex surface of the projecting member is about twice the length of the projecting member.